Conservation of Ancient Timbers from the Sea 299
5 Conservation Methods
The following discussion deals with different conservation methods under a
number of headings in relation to their application for the conservation of
small and large wooden objects. The main headings comprise: (i) PEG treat-
ments, (ii) in-situpolymerisation, (iii) freeze drying, and (iv) air drying. Before
commencing a treatment it is necessary to remove or neutralise contaminants
that enter the object through long-term exposure to seawater and the burial
sediments.
5.1 Removal of Mineral Inclusions
Salts are passively absorbed into wooden objects in seawater, but some ions
notably iron(III) are actively bound by cellulose, and high concentrations
of iron corrosion products build up in consequence. As the wood becomes
anoxic, these salts are converted into sulfides by the activity of SRB. A phys-
ical consequence of iron inclusions is that the wood microstructure becomes
blocked making the object impermeable to future conservation treatments.
Iron sulfide is unstable in the aerobic environment, and its oxidation can
destroy the object (Figure 17).
Figure 17Kidney dagger handle from the Mary Rose with salt formation on surface